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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79e21ef2e74a4e19a9945d99a527bf3df97e6135bf2d01a0a256a814ab53a894' 
  AND token = 'xtYkkWtLf5zBpwNkhf3vtOCXSwzKMPtQYv2w9KDReYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}